Surface Cell Density Research Articles

Fabrication of stable slippery lubricant-infused porous surface on polymethyl methacrylate/thermoplastic polyurethane by supercritical CO2 foaming

The development of sustainable and efficient methods to prepare slippery lubricant-infused porous surface (SLIPS) is a profound work. In this study, using bilayer polymers restricting foaming mutually, bimodal cells were prepared through bilayer poly(methyl methacrylate) (PMMA). At the same time, uniform cells were prepared by bilayer PMMA /thermoplastic polyurethane (TPU). The prepared porous surfaces exhibited a high porosity (57% or more). TPU as dispersed phase increased the cell density of the PMMA/TPU surface with a maximum cell density of 5.5 × 107 cells/cm2 and an average cell size of 1.0 μm. SLIPS prepared on PMMA/TPU surface with high porosity and uniform microcellular had better stability, and the sliding angle (SA) remained less than 10° after centrifugal rotation at 8000r/min. Therefore, this work provides an approach to improve the surface cell density and produce SLIPS sustainably and efficiently.

Surrogate vascular input function measurements from the superior sagittal sinus are repeatable and provide tissue-validated kinetic parameters in brain DCE-MRI

Accurate vascular input function (VIF) derivation is essential in brain dynamic contrast-enhanced (DCE) MRI. The optimum site for VIF estimation is, however, debated. This study sought to compare VIFs extracted from the internal carotid artery (ICA) and its branches with an arrival-corrected vascular output function (VOF) derived from the superior sagittal sinus (VOFSSS). DCE-MRI datasets from sixty-six patients with different brain tumours were retrospectively analysed and plasma gadolinium-based contrast agent (GBCA) concentration-time curves used to extract VOF/VIFs from the SSS, the ICA, and the middle cerebral artery. Semi-quantitative parameters across each first-pass VOF/VIF were compared and the relationship between these parameters and GBCA dose was evaluated. Through a test–retest study in 12 patients, the repeatability of each semiquantitative VOF/VIF parameter was evaluated; and through comparison with histopathological data the accuracy of kinetic parameter estimates derived using each VOF/VIF and the extended Tofts model was also assessed. VOFSSS provided a superior surrogate global input function compared to arteries, with greater contrast-to-noise (p < 0.001), higher peak (p < 0.001, repeated-measures ANOVA), and a greater sensitivity to interindividual plasma GBCA concentration. The repeatability of VOFSSS derived semi-quantitative parameters was good to excellent (ICC = 0.717–0.888) outperforming arterial based approaches. In contrast to arterial VIFs, kinetic parameters obtained using a SSS derived VOF permitted detection of intertumoural differences in both microvessel surface area and cell density within resected tissue specimens. These results support the usage of an arrival-corrected VOFSSS as a surrogate vascular input function for kinetic parameter mapping in brain DCE-MRI.

Fabrication of skinless cellular poly (vinylidene fluoride) films by surface-constrained supercritical CO2 foaming using elastic gas barrier layers

Removing the solid skin of polymer foams is a challenging approach for supercritical carbon dioxide (scCO2) foaming. Herein, a surface-constrained foaming method was used to fabricate skinless cellular poly (vinylidene fluoride) (PVDF) films. The use of organosilicone and nature latex as gas barrier layers resulted in low CO2 diffusion rates of 2.16 × 10−11 m2/s and 4.73 × 10−13 m2/s, and trigger heterogeneous nucleation of cells on the PVDF/barrier layer interface. The skin layer and the cell size gradient in the region close to the surface were successfully eliminated, and the surface cell density and cell size could be controlled in the range of 7.2 × 106 cells/cm3, and 13–41 µm, respectively. Moreover, the fabricated skinless cellular PVDF films exhibited an enhanced melting temperature and crystallinity due to the plasticizing effect of scCO2. The present study provides new thoughts for the fabrication of skinless polymer films using surface-constrained scCO2 foaming.

Influence of surface coatings on the adhesion of Shewanella oneidensis MR-1 to hematite

The adhesion of dissimilatory iron reducing bacteria (DIRB) to iron oxides is an important process to initiate direct extracellular electron transfer. Iron oxides in natural environments are often coated by organic matter or silica (SiO2) which alters their surface physicochemical properties. To investigate the influence of these surface coatings, we characterized the dynamic adhesion processes of Shewanella oneidensis MR-1 to bare hematite, humic acid-coated hematite (hematite-HA), and SiO2-coated hematite (hematite-SiO2) using Quartz Crystal Microbalance with Dissipation (QCM-D). The molecular-level process and mechanism were investigated using in situ Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectrometry. We found that MR-1 formed a rigid bacterial layer on bare hematite. Coating with HA or SiO2 decreased the surface cell density during the initial adhesion stage, and compromised the stability of the subsequent bacterial attachment. The FTIR combined with two-dimensional correlation spectroscopy (2D-COS) analysis showed that C-moieties of polysaccharides dominated interactions in initial adhesion on HA and SiO2-coated hematite. In the longer term, the HA coating hindered the adsorption of amide, but promoted the binding of polysaccharide C-moieties to hematite. We concluded that, in general, both the HA and SiO2 coatings reduced the attachment of MR-1 on hematite. These results advance our understanding of the roles of surface coatings on microbe-mineral interactions, which has significant implications for a series of biogeochemical processes in nature.

CD205+ polymorphonuclear myeloid-derived suppressor cells suppress antitumor immunity by overexpressing GLUT3.

Myeloid‐derived suppressor cells (MDSCs) are responsible for antitumor immunodeficiency in tumor‐bearing hosts. Primarily, MDSCs are classified into 2 groups: monocytic (M)‐MDSCs and polymorphonuclear (PMN)‐MDSCs. In most cancers, PMN‐MDSCs (CD11b+Ly6ClowLy6G+ cells) represent the most abundant MDSC subpopulation. However, the functional and phenotypic heterogeneities of PMN‐MDSC remain elusive, which delays clinical therapeutic targeting decisions. In the 4T1 murine tumor model, CD11b+Ly6Glow PMN‐MDSCs were sensitive to surgical and pharmacological interventions. By comprehensively analyzing 64 myeloid cell‐related surface molecule expression profiles, cell density, nuclear morphology, and immunosuppressive activity, the PMN‐MDSC population was further classified as CD11b+Ly6GlowCD205+ and CD11b+Ly6GhighTLR2+ subpopulations. The dichotomy of PMN‐MDSCs based on CD205 and TLR2 is observed in 4T07 murine tumor models (but not in EMT6). Furthermore, CD11b+Ly6GlowCD205+ cells massively accumulated at the spleen and liver of tumor‐bearing mice, and their abundance correlated with in situ tumor burdens (with or without intervention). Moreover, we demonstrated that CD11b+Ly6GlowCD205+ cells were sensitive to glucose deficiency and 2‐deoxy‐d‐glucose (2DG) treatment. Glucose transporter 3 (GLUT3) knockdown by siRNA significantly triggered apoptosis and reduced glucose uptake in CD11b+Ly6GlowCD205+ cells, demonstrating the dependence of CD205+ PMN‐MDSCs survival on both glucose uptake and GLUT3 overexpression. As GLUT3 has been recognized as a target for the rescue of host antitumor immunity, our results further directed the PMN‐MDSC subsets into the CD205+GLUT3+ subpopulation as future targeting therapy.

Wind induced turbulence caused colony disaggregation and morphological changes in the cyanobacterium &lt;i&gt;Microcystis&lt;/i&gt;

微囊藻群体大小和形态决定其垂向迁移能力，从而影响着水华的形成.为了探讨湖泊中风生紊流对微囊藻群体大小和形态的影响，本研究于2012年8月26日至9月7日在太湖梅梁湾的围隔内进行了12 d的昼夜不间断的高频采样（采样间隔每2小时一次）.研究期间，水面微囊藻密度呈现4次周期性消涨，藻密度变化范围为4×10⁴~2671×10⁴ cells/mL.而整个水柱中的藻密度变化范围仅为3×10⁴~18×10⁴ cells/mL.皮尔逊相关性分析表明微囊藻的原位生长速率与表面藻密度呈负相关而与风速呈正相关.强风速使微囊藻在水柱中均匀分散，增强了透光性，促进了微囊藻的生长.微囊藻群体粒径随着风速的增大逐渐减小，反之亦然.其中值粒径（D₅₀）变化范围为66.2~768.0 μm.在此期间微囊藻群体形态主要以鱼害微囊藻、不规则的惠氏微囊藻、球状的惠氏微囊藻和铜绿微囊藻群体形态为主，其占比也呈现出波动状态.皮尔逊相关分析结果显示微囊藻群体大小与风速呈负相关，说明湖泊中风生紊流会影响微囊藻群体大小.当紊流强度为2.33×10^-5 m²/s³时，微囊藻群体会发生破碎现象，该紊流强度相当于5 m/s的风在30 m深的水库或湖泊中所产生的紊流强度.微囊藻群体被风生紊流破碎后最大粒径与该风速下紊流的最小涡旋尺度相近，表明紊流的最小涡旋尺度决定了微囊藻所能形成群体的最终大小.监测期间，整水柱中不同群体形态的微囊藻占比发生了明显变化，在监测初期以鱼害微囊藻群体形态为主，随后不规则的惠氏微囊藻和铜绿微囊藻群体形态的比例不断增加，最后鱼害微囊藻群体形态又占据主导地位.球状的惠氏微囊藻群体形态在整个监测期中的比例随时间的增加而逐渐降低.不同群体形态微囊藻之间比例的大幅变化无法用微囊藻生长演替来解释.而皮尔逊相关分析结果显示鱼害微囊藻与惠氏微囊藻（不规则的和球状的惠氏微囊藻之和）群体形态之间存在负相关，且惠氏微囊藻与铜绿微囊藻群体形态呈负相关.但在今后研究中需进一步关注在微囊藻群体形态的动态变化过程中细胞大小、胶被、产毒特性和基因序列等特征，从而验证不同种微囊藻群体是否存在形态转换这一猜想.总而言之，普通强度的风生紊流能够破碎微囊藻群体，而气候变化导致的内陆湖泊周边风速下降会促使微囊藻形成更大的群体，从而有利于水华的形成.;Colony size and morphology influence the vertical migration capacity of Microcystis and therewith the occurrence of surface accumulations or blooms. To explore the influence of wind-induced turbulence on the colony size and morphology of Microcystis in field conditions, a high-frequency field investigation was conducted in an enclosure in Meiliang Bay, Lake Taihu, China, from 26 August to 7 September 2012. A Pearson's correlation analysis indicated that the in situ growth rate of Microcystis was negatively related to surface cell density and positively related to wind speed. Strong wind speed stimulated Microcystis growth by enhancing light transmission due to the homodispersion of Microcystis in the water column. The Microcystis colony size was negatively correlated with wind speed, suggesting that wind-induced turbulence could break up colonies in shallow lakes. The results indicated that Microcystis colonies could be broken up by a turbulence intensity of 2.33×10^-5 m²/s³, which corresponds to an average wind speed of 5.00 m/s in a reservoir with 30-m depth. Different Microcystis morphotypes were present and negative relationships were detected between the proportion of Microcystis ichthyoblabe and the proportion of Microcystis wesenbergii and between the proportion of Microcystis aeruginosa and the proportion of Microcystis wesenbergii out of all Microcystis throughout the water column, but more evidence is need to support the hypothesis that the morphology of Microcystis colonies changes over time. Altogether, the results suggest that declining wind speed, driven by climate change, will promote surface blooms of Microcystis due to the formation of larger colonies.

Structural modifications and thermodynamic characteristics of calcite growth during interaction with biomolecular glycine: new insights into biogenesis

Extensive studies have led to a common understanding of how organic molecules affect the phase, morphology and crystal structure of carbonate minerals. However, further analyses of crystal structures and the unique thermal decomposition characteristics of calcite affected by glycine have rarely been reported. Here, glycine was added as an additive to investigate the biomimetic mineralization of calcites at different glycine concentrations and pH values by virtue of the titration method. The sample characteristics were first analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and laser grain size analysis to investigate the morphology, crystal structure and grain size distribution, respectively. The results indicate that the precipitates are calcites, although SEM and XRD analyses indicated significant differences regarding surface morphology, cell density and cell volume. In addition, taking into account the complexation of Ca2+ with glycine, the samples removed from the precipitation system at different time intervals also confirm the presence of vaterite. More importantly, comparative studies of thermal decomposition between calcites under different conditions were carefully investigated using thermogravimetric analysis at different heating rates of 5, 10, 20, and 30 °C min−1 from 100 to 1000 °C. The kinetic parameters of average activation energy (E) and pre-exponential factor (A) were calculated by the Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose methods to verify that the calcite has a lower crystallinity, activation energy and enthalpy change (ΔH) with glycine incorporation. Thus, this study provides important new insight into the effects of glycine in inducing the biomimetic mineralization of calcite, especially the crystal structural and thermodynamic characteristics.

Analysis of the Corneal Anterior and Posterior Surface in Patients With Peripheral Hypertrophic Subepithelial Corneal Opacification.

To characterize the corneal changes in peripheral hypertrophic subepithelial corneal opacification (PHSCO) considering elevation of the anterior and posterior corneal surface, corneal astigmatism, tear secretion, and endothelial cell density. Thirty-eight eyes of 22 patients with PHSCO on at least 1 eye and 38 eyes of 22 age- and sex-matched healthy subjects were included in this retrospective cross-sectional study. Using the Pentacam system (Oculus, Wetzlar, Germany), measurement of the anterior and posterior corneal surface was performed. In addition, the Schirmer test was conducted, and endothelial cells were counted in the central cornea with a specular microscope (SP-3000P; Topcon, Tokyo, Japan). The mean age was 55.2±11.7 years in patients with PHSCO and 54.1±12.4 years in healthy subjects. The corneas of patients with PHSCO showed higher corneal astigmatism of both the corneal anterior and posterior surface (2.9/0.5 vs. 0.8/0.3 D, PHSCO vs. controls, P=<0.001/<0.01). The cornea was thickest in the peripheral 12-o'clock position and the peripheral superior nasal area. Remarkably, central endothelial cell density was markedly reduced in patients with PHSCO (2,372.6 cell/mm±328.1 vs. 2,673 cells/mm±287.6, P<0.01, PHSCO vs. controls). Also, the Schirmer test revealed lower tear secretion in patients with PHSCO (9.8±4.4 mm vs. 14.3±5.7 mm, P<0.001, PHSCO vs. controls). The astigmatism of both the anterior and posterior corneal surface is increased in patients with PHSCO. Intriguingly, tear secretion and central endothelial cell density are reduced in patients with PHSCO. These measurements may become useful to assess the impact of morphological changes on vision and to track disease progression in PHSCO.

The Basal Layer of the Epidermis: A Mathematical Model for Cell Production Under a Surface Density Constraint

An age-structured model for the cell populations of the epidermis basal layer is proposed, with the aim of quantifying the cell production which makes possible epidermis renewal. The model, which extends our previous model [J. Math. Biol., 73 (2016), pp. 1595--1626], describes the dynamics of proliferating cells, differentiated cells, and apoptotic cells under the physical constraint on the total surface cell density imposed by the cell occupancy of a basement membrane. To fulfill this constraint during any dynamics, the surface cell density is assumed to control cell migration toward the epidermis suprabasal region, as well as the balance between production of proliferating and of differentiated cells at cell division. The well-posedness of the model is fully studied, and the unique steady state is characterized. Numerical simulations are provided for realistic values of the parameters, giving some insight into the stability of the equilibrium and into the homeostatic properties of the model.

Thermal joining of foamed thermoplastic injection-moulded parts using laser radiation

The foam injection moulding is an established process to produce plastic components with reduced density. Due to the fragile foam structure, contactless welding methods such as laser transmission welding are suitable for foamed components. In a research project, the correlation between the injection moulding parameters and the resulting foam structure is determined in preliminary tests. Specimens with four different foam structures are produced, which differ in terms of their surface layer thickness and cell density. Measurements of the transmittance, as well as the intensity profile after irradiation of the transparent specimen, show that the transmission of the foamed test specimens is lower than compared to compact specimens. In particular, foam structures with low cell density and low surface layer thickness show a low transmittance. The weld strength is influenced only by the foam structure of the transparent joining partner. Additionally, a possible post-expansion of the enclosed gas during the welding process has to be taken into account. The temperature within the laser-absorbing joining partner is locally increased above the melting point of the plastic. Once the surrounding material is melted, the gas can expand due to the temperature increase and defects during the solidification of the melt are formed.

Platelet-rich plasma induces post-natal maturation of immature articular cartilage and correlates with LOXL1 activation

Platelet-rich plasma (PRP) is used to stimulate the repair of acute and chronic cartilage damage even though there is no definitive evidence of how this is achieved. Chondrocytes in injured and diseased situations frequently re-express phenotypic biomarkers of immature cartilage so tissue maturation is a potential pathway for restoration of normal structure and function. We used an in vitro model of growth factor-induced maturation to perform a comparative study in order to determine whether PRP can also induce this specific form of remodeling that is characterised by increased cellular proliferation and tissue stiffness. Gene expression patterns specific for maturation were mimicked in PRP treated cartilage, with chondromodulin, collagen types II/X downregulated, deiodinase II and netrin-1 upregulated. PRP increased cartilage surface cell density 1.5-fold (P < 0.05), confirmed by bromodeoxyuridine incorporation and proportionate increases in proliferating cell nuclear antigen gene expression. Atomic force microscopy analysis of PRP and growth factor treated cartilage gave a 5-fold increase in stiffness correlating with a 10-fold upregulation of lysyl oxidase like-1 gene expression (P < 0.001). These data show PRP induces key aspects of post-natal maturation in immature cartilage and provides the basis to evaluate a new biological rationale for its activity when used clinically to initiate joint repair.

Nano-textured fluidic biochip as biological filter for selective survival of neuronal cells.

This is an innovative study to engineer biological filter to evaluate the effect of template surface structure and physiochemical properties that can be used for wide variety of applications in biological, health care as well as environmental protection. Specifically, planar silicon (Si) wafer and arrayed Si nano-tips (SiNT) templates were fabricated and coated with gold for various lengths of time to study the effect of surface charge, surface roughness, and hydrophilicity on biological activity of rat pheochromocytoma cell lines PC12. The initial growth and proliferation of PC12 cells on Si and SiNT templates showed an antipathy for the ultra-sharp SiNTs templates. In contrast, the same cells demonstrated a preferable adherence to and proliferation on planar Si templates, resulting in higher cell densities by three orders of magnitude than those on SiNT templates. It is hypothesized that SiNTs array does generate nano-fluidic effect such that the effective contact region for aqueous solution on SiNTs is lower than that on planar Si templates, thus decreasing adsorbable area for cell viability and survival. Moreover, the effect of the gold coating on cell number density was analyzed in terms of the surface roughness, zeta potential and wetting properties of the templates. It was determined that surface charge, as measured by the zeta potential, strongly correlated with the trend observed in the surface cell density, whereas no such correlation was observed for surface roughness or wetting properties in the ranges of our experiment conditions.

Adhesion of Pseudomonas putida onto kaolinite at different growth phases

Bacterial adhesion to minerals in soils and sediments is of fundamental importance in mineral weathering and formation, soil aggregate stability, organic matter degradation and the fate of pollutants. Bacterial surface properties are considered to govern adhesion, and these properties likely change as a function of bacterial growth phase. However, the effect of growth stage on bacterial adhesion to clay minerals remains unclear. This work examined the influence of growth phase on the adhesion of Pseudomonas putida to kaolinite-coated coverslips. Fluorescence microscopy, together with a bacterial viability stain, was used to directly quantify surface cell density and viability of adhered P. putida. In situ attenuated total reflectance Fourier transform infrared spectroscopy was applied to yield molecular information about the characteristics of the bacteria, and the adsorption and desorption kinetics. Stationary-phase cells exhibited a higher adsorption density on kaolinite surfaces than mid-exponential-phase cells under static deposition conditions. Compared with the mid-exponential-phase cells, the stationary-phase cells displayed higher saturation coverage, and we fitted the results using a pseudo-first-order kinetics equation. The greater extent of adhesion of the stationary-phase cells was probably due to their smaller cell size and less negative surface charges compared with the cells from other growth stages, which resulted in deeper secondary energy minima and lower energy barriers for adhesion. The results from this study suggest that growth phase may strongly influence cell mobility and biofilm formation in aqueous geochemical environments.

Influence of relative low gas counter pressure on melt foaming behavior and surface quality of molded parts in microcellular injection molding process

A complex medical instrument exterior shell was chosen as a studying object to investigate the influence of relative low (&lt;10 MPa) gas counter pressure process on microcellular injection molding process. The gas counter pressure microcellular injection mould and related experiments were designed. The relative low gas counter pressure under which the melt can foam was mainly considered to improve the surface quality of molded parts without significantly prolonging production cycle. The effects of the gas counter pressure parameters on the surface quality, cell morphology, and cell density of microcellular parts were studied. A critical melt flow front pressure to effectively eliminate surface swirl marks of microcellular injection molded part was proposed. The mechanism of the influence of gas counter pressure process on foaming behavior of melt in filling process was analyzed. The reasonable gas counter pressure parameters to improve surface quality of products without significantly increasing molding cycle were obtained. By using the obtained reasonable gas counter pressure parameters, a sound microcellular injection molded product was injected finally.

Correction to Surface Cell Density Effects onEscherichia coliGene Expression during Cell Attachment

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to Surface Cell Density Effects on Escherichia coli Gene Expression during Cell AttachmentMeagan S. Mauter, Aaron Fait, Menachem Elimelech, and Moshe Herzberg*Cite this: Environ. Sci. Technol. 2013, 47, 15, 8991Publication Date (Web):July 12, 2013Publication History Published online12 July 2013Published inissue 6 August 2013https://doi.org/10.1021/es402943nCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views275Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (111 KB) Get e-Alerts Get e-Alerts

Surface Cell Density Effects on Escherichia coli Gene Expression during Cell Attachment

Escherichia coli attachment to a surface initiates a complex series of interconnected signaling and regulation pathways that promote biofilm formation and maturation. The present work investigates the effect of deposited cell density on E. coli cell physiology, metabolic activity, and gene expression in the initial stages of biofilm development. Deposited cell density is controlled by exploiting the relationship between ionic strength and bacterial attachment efficiency in a packed bed column. Distinct differences in cell transcriptome are analyzed by comparing sessile cultures at two different cell surface densities and differentiating ionic strength effects by analyzing planktonic cultures in parallel. Our results indicate that operons regulating trypotophan production and the galactitol phosphotransferase system (including dihydroxyacetone phosphate synthesis) are strongly affected by cell density on the surface. Additional transcriptome and metabolomic impacts of cell density on succinate, proline, and pyroglutamic acid systems are also reported. These results are consistent with the hypothesis that surface cell density plays a major role in sessile cell physiology, commencing with the first stage of biofilm formation. These findings improve our understanding of biofilm formation in natural and engineered environmental systems and will contribute to future work ranging from pathogen migration in the environment to control of biofouling on engineered surfaces.

Role of outer membrane c‐type cytochromes MtrC and OmcA in Shewanella oneidensis MR‐1 cell production, accumulation, and detachment during respiration on hematite

The iron-reducing bacterium Shewanella oneidensis MR-1 has the capacity to contribute to iron cycling over the long term by respiring on crystalline iron oxides such as hematite when poorly crystalline phases are depleted. The ability of outer membrane cytochromes OmcA and MtrC of MR-1 to bind to and transfer electrons to hematite has led to the suggestion that they function as terminal reductases when this mineral is used as a respiratory substrate. Differences in their redox behavior and hematite-binding properties, however, indicate that they play different roles in the electron transfer reaction. Here, we investigated how these differences in cytochrome behavior with respect to hematite affected biofilm development when the mineral served as terminal electron acceptor (TEA). Upon attachment to hematite, cells of the wild-type (WT) strain as well as those of a ΔomcA mutant but not those of a ΔmtrC mutant replicated and accumulated on the mineral surface. The results indicate that MtrC but not OmcA is required for growth when this mineral serves as TEA. While an OmcA deficiency did not impede cell replication and accumulation on hematite prior to achievement of a maximum surface cell density comparable to that established by WT cells, OmcA was required for efficient electron transfer and cell attachment to hematite once maximum surface cell density was achieved. OmcA may therefore play a role in overcoming barriers to electron transfer and cell attachment to hematite imposed by reductive dissolution of the mineral surface from cell respiration associated with achievement of high surface cell densities.

Ocular Manifestations of Trichothiodystrophy

Trichothiodystrophy (TTD) is a rare, autosomal recessive disorder characterized by sulfur-deficient brittle hair and multisystem abnormalities. Many TTD patients have a defect in known DNA repair genes. This report systematically evaluates the ocular manifestations of the largest-to-date cohort of TTD patients and xeroderma pigmentosum (XP)/TTD patients. Case series. Thirty-two participants, ages 1 to 30 years, referred to the National Eye Institute for examination from 2001 to 2010; 25 had TTD and 7 had XP/TTD. Complete, age- and developmental stage-appropriate ophthalmic examination. Visual acuity (VA), best-corrected VA, ocular motility, state of the ocular surface and corneal endothelial cell density, corneal diameter, and lens assessment. Developmental abnormalities included microcornea (44% TTD), microphthalmia (8% TTD, 14% XP/TTD), nystagmus (40% TTD), and infantile cataracts (56% TTD, 86% XP/TTD). Corrective lenses were required by 65% of the participants, and decreased best-corrected VA was present in 28% of TTD patients and 71% of XP/TTD patients. Degenerative changes included dry eye (32% TTD, 57% XP/TTD) and ocular surface disease identified by ocular surface staining with fluorescein (32% TTD) that usually are exhibited by much older patients in the general population. The 2 oldest TTD patients exhibited clinical signs of retinal/macular degeneration. Four XP/TTD patients presented with corneal neovascularization. These TTD and XP/TTD study participants had a wide variety of ocular findings including refractive error, infantile cataracts, microcornea, nystagmus, and dry eye/ocular surface disease. Although many of these can be ascribed to abnormal development--likely owing to abnormalities in basal transcription of critical genes--patients may also have a degenerative course. Proprietary or commercial disclosures may be found after the references.

The estimation of cell density in isotropic microcellular polymeric foams using the critical bubble lattice

In this study, models for estimating the cell density of isotropic polymeric foams using the surface cell density were developed. The basic morphological unit cell for these models is a gas-filled pentagonal dodecahedral cell cavity. The critical bubble lattice model was introduced to associate the packing structure of the pentagonal dodecahedral cells with a face-centered cubic (FCC) packing structure, and the cell density was estimated. This model was then used to investigate the effect of nonperfect cell cross-sections as found in the micrographs of cell densities of foams. Two cases were examined: first, the ideal case of a perfect cross-section, and second, the actual case of a nonperfect cross-section. The plots of cell density versus surface cell density from recently published data show the effect of a nonperfect cross-section on the estimation of cell density within an FCC lattice with perfect and nonperfect cell cross-sections. The percentage average absolute deviation (AAD) showed that the nonperfect cell cross-sectional model reliably predicts the cell density of isotropic low-density foam with an AAD of 39.2%. The perfect cell cross-sectional model reliably predicts the cell density of isotropic high-density foam with an AAD of 57.2%. These new models are more reliable than the conventional model, which give AADs 59.4% for low-density foams and 62.4% for high-density foams. Furthermore, the isotropic foam index was introduced as a parameter to indicate the isotropic foam behavior.

Mouse Fibroblast Cell Adhesion Studied by Neutron Reflectometry

Neutron reflectometry (NR) was used to examine live mouse fibroblast cells adherent on a quartz substrate in a deuterated phosphate-buffered saline environment at room temperature. These measurements represent the first, to our knowledge, successful visualization and quantization of the interface between live cells and a substrate with subnanometer resolution using NR. NR data, attributable to the adhesion of live cells, were observed and compared with data from pure growth medium. Independently of surface cell density, the average distance between the center of the cell membrane region and the quartz substrate was determined to be ∼180 Å. The membrane region (∼80 Å thick) contains the membranes of cells that are inhomogeneously distributed or undulating, likely conforming to the nonplanar geometry of the supporting adherence proteins. A second region of cell membranes at a greater distance from the substrate was not detectable by NR due to the resolution limits of the technique employed. Attachment of the live cell samples was confirmed by interaction with both distilled water and trypsin. Distinct changes in the NR data after exposure indicate the removal of cells from the substrate.